Shinobi yoru Koi wa Kusemono

Kanade Kazamaki is Shinobi trained and brought up with the Toujo family, being Keigo Tojou's childhood friend. Defeating the Toyoda family who has reigned over the Tojou family, Kanade joins Keigo at an all boys school where the future head of the Toyoda family, Eishi Toyoda attends... But what is this about Kanade being Eishi Toyoda's first love?